Recently, a system where a plurality of unspecified people upload contents such as text, an image, a moving picture, etc. via a cyber space such as the Internet, and open the contents to other people so that various contents are shared, is widely used.
In addition, a service where a different user posts comments on contents posted by a specific user, so that one's opinion related to the relevant contents may be shared, is widely distributed and actively used among lots of on-line users.
However, according to the conventional system, only service subscribers may share comments related to currently reproduced contents, and ordinary people who have not subscribed to a service cannot share comments.